The use of high pressure jets to entangle fibers in a nonwoven web, sometimes called hydroentangling, hydraulic needling or spunlacing, is known. Typically, these processes are used with carded nonwoven webs, although there is some hydraulic needling of wet laid nonwoven webs and spunbonded nonwoven webs. These processes support the nonwoven web on a highly porous member such as a mesh belt or a metal screen so that the high pressure fluid can pass through the nonwoven web and continue through the porous member for collection. A negative pressure (vacuum) is typically applied to the porous member to help draw fluid from the nonwoven web through the support member.
It is known to produce a patterned nonwoven fabric having entangled nonwoven fibers. U.S. Pat. No. 4,718,152 is directed to a method for production of patterned nonwoven fabric in which a fibrous web is subjected to high energy treatment with high velocity water streams not only for entangling the fiber but also for patterning the fibrous web. This latter process is sometimes called hydropatterning. The fiber entangling treatment is performed on a plurality of non-porous supports arranged in a multi-stage manner at regular intervals along the path of the fibrous web. The patterning treatment is performed on a separate non-porous support arranged downstream of the non-porous supports upon which fiber entangling takes place. For the precursor webs described in this patent, both sides of the web are the same.
It would be useful to provide an improved patterned nonwoven material and an efficient method for its production. In particular, it would be useful to provide sided nonwovens which are often preferred as wiping substrates.